The anomeric specificities of several aldose-ketose isomerases have been correctly predicted from mechanistic studies. This will be extended to glucuronic acid isomerase. Active site reagents will be synthesized for several isomerases. The stereochemistry of enzymes that use an enolpyruvate intermediate in their mechanisms will be established. Carbon-14 primary isotope effects and tritium secondary isotope effects will be used in the study of glycoside cleavage reactions and carboxybiotin reactions.